1. Field of the Invention
The present invention relates to an on-vehicle navigation system, and particularly relates to an on-vehicle navigation system for supporting driving by using a special lane such as a carpool lane or the like.
2. Description of the Invention
Conventionally, in an on-vehicle navigation system, after searching a recommended route from a current position to a destination by using a route calculation method such as Dijkstra's method, route guidance of a vehicle from the current position to the destination has been performed along the searched recommended route. In this type of on-vehicle navigation system, before searching a recommended route, search conditions for a recommended route, such as use of an expressway, can be previously set by user operation, and a user was able to receive route guidance along a recommended route satisfying the set search conditions.
Highways (or freeways) in large cities of the U.S. can include a special lane that is called a carpool lane together with a normal lane.
The carpool lane is a lane provided for removing a traffic jam, reducing exhaust gas, decreasing commuting time or the like; and public buses, cars and motorcycles with two or more passengers (specified number of passengers is different among states) can use the lane. Hybrid cars can also use the lane even in the case of one passenger when they apply to the motor vehicle official of a state government agency and permission is granted. However, if a vehicle that does not satisfy such restrictions enters the carpool lane, it is fined for a violation. Legal advancing from the normal lane to the carpool lane is authorized only from a predetermined advancing authorized section (in other words, entrance), and legal exiting to the normal lane is authorized only from a predetermined exiting authorized section (in other words, exit). Note that the exiting authorized section and the advancing authorized section are usually regarded as the same (in other words, a unified entrance/exit) in the carpool lane.
Some on-vehicle navigation systems capable of setting whether such a carpool lane should be used as a search condition of a recommended route have been suggested, such as Japanese Patent Laid-Open No. 2001-183159 and Japanese Patent Laid-Open No. 2006-138798. However, in order to confirm the exiting authorized section and the advancing authorized section of the carpool lane in actual driving, the user must depend on the difference in lane indications or the existence of small markings. This makes it difficult to actually confirm the exiting authorized section and advancing authorized section in many cases.
Thus, even if route guidance allowing the vehicle to exit from the carpool lane to the normal lane through the exiting authorized section along the recommended route was performed, the user may miss the exiting authorized section. If such a situation occurs near an interchange or an exit from the highway on the recommended route, the vehicle is prevented from moving toward the interchange point or the exit of highway, and thus the vehicle deviates considerably from the recommended route. Further, even in the case where the vehicle succeeds in exiting the carpool lane at the exiting authorized section, it may be difficult to move from the exiting authorized section to the interchange point or the highway exit because of the number or width of normal lanes.
Further, in the case where a search condition to preferentially drive in the carpool lane was set in a conventional on-vehicle navigation system, route guidance using the carpool lane as a recommended route was performed to the interchange point or the highway exit after the vehicle advanced to the highway, but there were cases where the vehicle missed the advancing authorized section because of the difficulty of confirming the advancing authorized section.
Such a difficulty of confirming the exiting authorized section and the advancing authorized section may give the user a sense of insecurity and interfere with safe driving. Therefore, there has been a problem that the user had difficulty in reliably performing desired driving using a special lane such as the carpool lane.